Several anti-cancer drugs have attained a certain degree of success during recent years. Amongst these there may be specifically mentioned compounds such as daunomycin, adriamycin, methotrexate, mithramycin, cytosine arabinoside, 6-azauridine and the like. All these are low-molecular-weight compounds and these can be conjugated to form novel drugs according to the present invention.
One of the drawbacks of such anti-cancer drugs is a comparatively high degree of toxicity of same. Thus it is hard in some cases to use adequate dosages as these are too toxic to the mammal being treated.
During recent years various attempts have been made to prepare specific antibodies towards tumors, but these have not given hitherto the desired anti-cancer effects. Certain antibodies selective to tumors have been complexed in a non-covalent manner to antitumor drugs in order to enhance the effectiveness of such drugs against tumor cells. These too have not given the desired results.